Bearing unit for the hub of a vehicle wheel equipped with a tire inflating system

ABSTRACT

A bearing unit comprises a radially outer stationary race ( 1 ) and a pair of radially inner rotatable half-races ( 2   a   , 2   b ). Au intermediate annular chamber ( 8 ) is defined between the outer race ( 1 ) and the inner half-races ( 2   a   , 2   b ) The intermediate chamber communicates with the outside through first air passages ( 5 ) formed in the outer race ( 1 ) and with the inside of the bearing unit through second radial air passages ( 6 ) defined between the inner half-races ( 2   a   , 2   b ). An intermediate annular member ( 10 ) is axially interposed between the inner half-races ( 2   a   , 2   b ) and defines the second passages ( 6 ).

TECHNICAL FIELD

The present invention refers to a bearing unit for the hub of a wheel ofa vehicle with an on-board tyre inflating system.

BACKGROUND

There are known bearing units for a vehicle wheel hub provided withspecial vents and sealing devices for blowing into the tyre airpressurized by a source of pressurized air mounted on board of thevehicle. These solutions allow to adjust and/or monitor the air pressurein the tyres.

For a better understanding of the state of the art and problems inherentthereto, there will be at first described a bearing unit of the abovementioned type, with reference to FIG. 1 of the accompanying drawings. Abearing unit of this kind is known, for example, from EP-713 021, EP-656267, U.S. Pat. No. 5,503,480, DE-37 38 529, FR-2 714 943.

In FIG. 1, a bearing unit comprises an outer race 1, an inner race 2formed by two axially adjacent half-races 2 a, 2 b and two sets ofbearing balls 3, 4 interposed between the outer race 1 and the innerhalf-races 2 a, 2 b. In a radial plane located between the two sets ofballs 3, 4 there are several outer radial ducts 5 passing through thebearing outer race 1, and several inner radial passages 6 obtainedthrough the inner bearing race 2. The inner passages 6 are generallydefined by the coupling of complementary recesses formed according to aspecular symmetry on facing surfaces of the two inner half-races 2 a, 2b.

Mounted in the annular space defined by the outer race 1, the inner race2 and the two sets of balls 3, 4 is a sealing device that allowspressurized air to pass through the outer 5 and inner 6 ducts of thebearing. The sealing device is constituted by two annular sealingmembers 7 facing one another axially and disposed symmetrically withrespect to the radial plane in which the ducts 5 and 6 of the bearingunit lie. The sealing members define an intermediate annular chamber 8.Air pressurized by a pressurized air source mounted on board of thevehicle, which may be part of an automatic system or a system controlledby the driver, passes through specials ducts obtained in the suspensionstandard of the wheel where the bearing is housed, passes through theouter ducts 5, in the intermediate annular chamber 8, through the innerducts 6, and from here is conveyed through other ducts to the wheel rimand finally the tyre.

SUMMARY

The object of the present invention is to allow to inflate pressurizedair to the wheel tyre through the hub, without having to formconventional radial bores or recesses in the inner half-races of thebearing. The formation of said bores involves a constructionalcomplication that may adversely affect the raceways of the bearingraces, which, as known, have very low admissible tolerances.

This and other objects and advantages, that will be better understood inthe following, are accomplished according to the invention by a bearingunit having one or more of the features as described herein.

Another object of the present invention is to improve the flow of airthrough the bearing, particularly through its rotating part.

DESCRIPTION OF THE DRAWINGS

There will now be described a few preferred, but not limitingembodiments of a bearing unit according to the invention, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a schematic axial cross-sectional view of a bearing unit ofknown kind for the hub of the wheel of a vehicle equipped with a tyreinflating system;

FIG. 2 is an schematic axial cross-sectional view of a bearing unitaccording to a first embodiment of the present invention;

FIG. 3 is a perspective view of an annular element which the bearingunit of FIG. 2 is provided with;

FIG. 4 is a perspective view of an annular member according to a secondembodiment of the invention;

FIG. 5 is schematic axial cross-sectional view of a bearing unitprovided with the annular member of FIG. 4;

FIG. 6 is a partial, schematic axial cross-sectional view of a bearingunit provided with an annular member according to a third embodiment ofthe invention;

FIG. 7 is a schematic radial cross-sectional view of an annular memberaccording to a fourth embodiment of the invention; and

FIG. 8 is a partial schematic axial cross-sectional view of a bearingunit provided with the annular member of FIG. 7.

Referring now to FIG. 2, a bearing unit for the hub of a vehicle wheelincludes an outer stationary race 1, two axially aligned innerhalf-races 2 a, 2 b, and two sets of rolling balls 3, 4 interposedbetween the outer race 1 and the inner half-races 2 a, 2 b.

DETAILED DESCRIPTION

The general arrangement of most of the elements of the bearing unitillustrated in FIG. 2 is generally known. Only the elements of specificimportance and interest for the purposes of the implementation of thepresent invention will therefore be described in detail in the followingdescription. For the construction of the parts and elements not shown indetail, reference may therefore be made to any of the above mentioneddocuments. Other constructional solutions may be found, for example, inU.S. Pat. No. 5,221,381, EP-521 719, U.S. Pat. No. 5,080,156, GB-2 223207, U.S. Pat. No. 4,844,138, EP-208 540. It is sufficient here toremind that in the stationary outer race 1 there is formed a passage 5through which the air coming from a source of pressurized air mounted onboard of the vehicle is let into an intermediate chamber 8 between therotating and fixed races of the bearing. The chamber 8 is delimitedlaterally by a pair of sealing members 7 fixed to the stationary race 1and in sliding contact with the half-races 2 a, 2 b.

An important characteristic of the solution according to the inventionis that between the inner half-races 2 a, 2 b there is axiallyinterposed an intermediate annular member 10 in which there are formedradial passages 6 that establish communication between the intermediatechamber 8 and the inner part of the bearing unit, from where the air isconveyed through other conduits (not shown) to the wheel rim and thenthe tyre.

In the embodiments of FIGS. 2 and 3 the passages 6 and the passages 5formed through the outer bearing race 1 lie substantially in the samecentral radial plane.

In the alternative embodiment of FIGS. 4 and 5, formed in the oppositeside faces of the annular member 10 are side recesses 6 a, 6 b which, inthe assembled condition of FIG. 5, defined radial passages 6 with theside faces of the respective adjacent half-race 2 a, 2 b.

As it will be appreciated, the half-races 2 a, 2 b are free ofconventional bores and recesses defining the radial passages of the typeindicated 6 in FIG. 1. Advantageously, this allows to

-   -   use inner half-races of standard design,    -   avoid further perforations and similar operations in the        finished half-races,    -   reduce manufacturing time for the half-races, and    -   avoid the risk of generating plastic deformation in the half        races, inadmissible for the low tolerances that the race ways        must exhibit.

The passage of air through the bearing unit according to the presentinvention takes place similarly as in bearing units of known kind.

In the embodiment shown in FIG. 6, the annular member 10 forms a pair ofopposite side flanges 11 a, 11 b extending in an axial direction forengaging the cylindrical surfaces of half-races 2 a, 2 b so as toprevent the annular member 10 from being separated from the rest of thebearing unit during transport and handling steps preceding theassembling on the hub.

With reference to FIGS. 7 and 8, according to another embodiment of theinvention, the annular member 10 forms a plurality of blade surfaces 12a, 12 b radially protruding in the intermediate annular chamber 8. Eachblade surface is inclined forwardly with respect to a direction ofrotation. The blade surfaces 12 a, 12 b are each disposed close to oneof the passages 6 and extend from an edge of the passage (here defined“trailing” edge with reference to a direction of rotation) towards theoutside and forwardly in such a direction of rotation. Owing to thisarrangement, when the inner half-races rotate fast with the hub, theblade surfaces capture air in the intermediate chamber 8 and convey itinto the passages 6 formed through the annular member 10. The annularmember 10 in this embodiment of the invention functions as an airconveyor rotor. In the preferred embodiment shown schematically in FIG.7, the blade surfaces comprise both surfaces 12 a inclined forwardlywith respect to the direction of rotation indicated by arrow A, andsurfaces 12 b inclined forwardly with respect to the opposite directionof rotation indicated by arrow B. A bearing unit provided with an airconveyor rotor of this type has the further advantage that it can beindifferently mounted on a wheel on the left or the right side of thevehicle. In one case, when the direction of rotation is that indicatedby arrow A, the air will be captured into chamber 8 by the surfaces 12a, and in the other case by the surfaces 12 b.

To improve the capturing of air to be conveyed through the bearing, theblade surfaces are preferably curved with a concavity facing one of thetwo possible directions of rotations.

It is to be understood that the invention is not limited to theembodiments here described and illustrated which are to be considered asexamples of a bearing units according to the invention. The invention islikely to undergo modifications as to the shape and location of parts,constructional and functional details, and materials employed. Forexample, the bearing units here shown are units of the so-called firstgeneration. However, reference to this possible field of use should notin any way be interpreted as limiting the scope of the patent, as theinvention is equally applicable to bearing units of the so-called secondor third generation with flanged races.

1. A bearing unit for a wheel hub of a vehicle equipped with a systemfor supplying pressurized air to a tire through the hub of the wheel,the bearing unit comprising: a radially outer stationary race, a pair ofradially inner rotatable half-races, an intermediate annular chamberbetween the outer race and the inner half-races, at least a first innerair passage formed through the outer race and communicating with theintermediate annual chamber, at least a second essentially radial innerair passage defined between the inner half-races and communicating withthe intermediate annular chamber; wherein the bearing unit furthercomprises an intermediate annular member axially interposed between theinner half races and defining at least partially said second passage,and wherein the intermediate annual member has a side face disposedadjacent to one of the two inner half-races, at least a side recessbeing formed in the side face, the side recess defining said at leastone second passage with the inner half-race adjacent to said side face.2. A bearing unit according to claim 1, wherein the half-races are freeof radial recesses or passages.
 3. A bearing unit according to claim 1 ,wherein the unit comprises at least two of said second passages and thatthe intermediate annular member has two opposite side faces each ofwhich is disposed adjacent to a respective inner half-race, at least aside recess being formed in each of said side faces so as to define oneof said second passages with the respective adjacent inner half-race.